I love all the FF soundtracks, and most non portable Castlevania scores are excellent. The Silent Hills soundtracks are pretty good to. As far as what's been mentioned- the metal gears have great music, but to me they're mostly only good while going to a scene, as are a lot of movie soundtracks, so they aren't something I would listen to outside the games. ODST does have a good sountrack but again something I probably wouldn't listen to outside the game itself. Mass Effect all in all has a great soundtrack to, but I wish the music wasn't so muted in the actual game, even with music volume all the way up.

Other good scores that come to mind- Super Metroid, Metroid Prime, Chrono Trigger and the always underappreciated Chrono Cross, Zelda TOOT, DKC 1 and 2, Starfox, the Katamaris, Suikoden, FF Tactics, the original Resident Evil, Shadow of the Colossus, and Oblivion.

One of my all time favorate video game tracks is one that didnt really have an offical game track. You just put the CD in your CD player, start track 2 and volla, music! The game being MechWarrior 2 and it's expansion MechWarrior 2: Ghost Bears Legacy (Ghost Beats ftw!!!)

Then there's also this tune that is one the creepiest tunes I've heard in a video game (to me anywho). It's from the ending of Freespace 2.